Anatomy: Basically, a starfish consists of a mouth and surrounding the mouth are rays.  On each of these rays there’re rows of small tube feet.  Around the mouth there is a central ring that is connected to all the tubes.  This ring is filled with water and it’s what makes the vascular system run. The system is what allows the starfish to move.

Characteristics: A distinct characteristic of Echinoderms is the radial symmetry.  It has several arms, 5 or more, that’s usually grouped with two on the left, one in the middle and two on the right.  The body is divided into five equal segments.  Each segment contains two sets of various internal organs.  Although they have some organs Echinoderms don’t have a heart, a brain, or eyes. Although a star fish’s mouth is situated on the top most other Echinoderms’ mouth is located on the underside. Echinoderms have an astonishing vascular system. This system supplies water through small muscular tubes to the tube feet.  These tube feet are tentacle-like structures with suction pads placed at their tips.  When any part of the tube feet presses against another moving object water is released from them resulting in a suction effect. When any amount of water is returned to the muscular tubes the suction is released.

Habitat: Mostly all of Echinoderms are organisms found in water environments. Echinoderms can usually be found from shallow waters at tide lines to deep in the sea. Although this is true some starfish are only found out at the deepest, muddiest parts of the ocean. Starfish are almost always found in the tropical oceans all around the world. Typically starfish are found in sand amongst coral reefs and rocky bottoms below tides. A starfish is a free-living organism. 

Importance: Although starfish might seem like they have no importance this isn’t the case.  The ecological relationships are sometimes very complex and starfish help maintain the balance of those relationships. Starfish are also very important in helping to sustain the balance of nature by thinning out biological excess.

Feeding: Starfish are carnivors but other Echinoderms vary in feeding habits.  Most star fish use their tube feet to extend itself inorder to extract its prey.  The most common prey star fish attack is claims. A tactic the star fish uses is once it has caught the shellfish, it slowly tries to pry open the shell so its muscles wear.  This will weaken the prey.  Star fish sometimes attack other small animals such as marine snails.

Respiration: An exchange between oxygen and carbon dioxide occur because a starfish has a water vascular system.  This means that through the tube feet working as gills oxygen can enter the system through the tube feet while carbon dioxide is exiting the body.

Internal Transportation: The starfish’ water vascular sytem is accountable for all of the transportation of the food, oxygen and waste products. 

Digestion/Excretion: The cardiac stomach and the pyloric stomach are responsible for the digestion of the starfish. The cardiac stomach, located at the center of the starfish is used to digest food.  In order for this to happen it must be pushed out of the organism’s body.  Sometimes a starfish will try to pry open the shell of its prey and inject their stomachs into their shells. If the starfish is successful in getting its stomach into the shell it will then digest the mollusk on the spot. After the starfish has finished eating the stomach will return back inside its body.  The almost digested food will then be moved to the pyloric stomach. To finish off the digestion process it is sometimes transported to the intestines. Waste will later be let out through the anus.

Reproduction: Echinoderms reproduction is sexual. It’s natural for a starfish to just spread their eggs and sperm into the water letting fertilization occur externally.  It only takes two hours for a female starfish to shed several million eggs into the water. A hollow ball called blastula will develop when matched with a sperm.  The starfish will change from a blastula to a larva to a miniature starfish. This whole process can take up to two months.

Interesting facts!

·     If a starfish was ever to loose its arm it would be capable of regenerating another one.

·      At the end of each of a starfish’ arm there is a microscope that lets the starfish see movement that is happening around it

·     There are almost 2000 different kinds of starfish!

Bibliography

1)       http://www.starfish.ch/reef/echinoderms.html

2)       http://www.adfg.state.ak.us/pubs/notebook/shellfsh/starfish.php

3)       http://www.allsands.com/science/animals/starfishinforma_vaa_gn.htm

4)       http://www.buzzle.com/articles/interesting-facts-about-starfish.html

5)       http://curiousanimals.net/animals/starfish/

6)       http://en.wikipedia.org/wiki/Starfish

7)       http://www.angelfire.com/ak2/mysticconnection/aa/starfish.html  

8)     http://egate.mcgehee.k12.la.us/faculty/jenniferz/biology/starfish%20B/STARFISH%20project/gen.%20anatomy.htm

Picture #1-http://en.wikipedia.org/wiki/File:Starfish_red_komodo.jpg

Picture #2- http://www.aims.gov.au/pages/reflib/cot-starfish/images/cot-fig13.gif